Self-Assembled Chiral Photonic Crystals From Colloidal Helices Racemate

TL;DR

This paper demonstrates a bottom-up self-assembly method for creating chiral photonic crystals from colloidal helices racemate, revealing structures with large photonic bandgaps and polarization selectivity, promising for photonic metamaterials.

Contribution

It introduces a simplified simulation approach to self-assemble chiral photonic crystals from colloidal helices racemate, showing potential for scalable photonic device fabrication.

Findings

Identified binary honeycomb and square lattice chiral crystals with opposite-handed helices.

Photonic calculations reveal large complete bandgaps in these chiral structures.

Square crystal exhibits dual polarization bandgaps for circularly polarized light.

Abstract

Chiral crystals consisting of micro-helices have many optical properties while presently available fabrication processes limit their large-scale applications in photonic devices. Here, by using a simplified simulation method, we investigate a bottom-up self-assembly route to build up helical crystals from the smectic monolayer of colloidal helices racemate. With increasing the density, the system undergoes an entropy-driven co-crystallization by forming crystals of various symmetries with different helical shapes. In particular, we identify two crystals of helices arranged in the binary honeycomb and square lattices, which are essentially composed by two sets of opposite-handed chiral crystal. Photonic calculations show that these chiral structures can have large complete photonic bandgaps. In addition, in the self-assembled chiral square crystal, we also find dual polarization bandgaps that selectively forbid the propagation of circularly polarized lights of a specific handedness along the helical axis direction. The self-assembly process in our proposed system is robust, suggesting possibilities of using chiral colloids to assemble photonic metamaterials.